Lake Warnock
Atchison County, Kansas38 acresView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Metals (other than mercury)
- #2 of 2 in the county
- Limited data
Lake Warnock in Atchison County, Kansas has a water quality grade of F (Algae-prone). Water clarity: 1.7 ft visibility. Phosphorus: 509.5 µg/L. Chlorophyll-a (algae): 219 µg/L. Surface area: 38 acres.
- Clarity
- 1.7 ft
- Area
- 38 acres
- Type
- Hypereutrophic
- Phosphorus
- 509.5 µg/L
- Chlorophyll-a
- 219 µg/L
- Trend
- ↑ Improving
Stays via Stay22
Stays near Lake Warnock
Compare lakeside cabins, hotels, and vacation rentals near Lake Warnock in Atchison County, Kansas — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Lake Warnock are listed below.
Top-rated places to stay near Lake Warnock
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Watch Lake Warnock’s letter
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Lake Warnock is a 38-acre highly nutrient-loaded hypereutrophic lake in Atchison County, Kansas. Water quality is graded F based on 2 sampling years through 2017. Overall water quality is improving over recent sampling years. Compared to the 1 other monitored lakes in Atchison County, Lake Warnock ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, KDHE, last sampled 2017-06-12. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The F is nutrients and algae, not a swimming clearance. Lake Warnock is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), pesticides, pH / acidity. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 1.7 ft of visibility. Phosphorus 509.5 µg/L. Chlorophyll-a 219 µg/L. TSI 82. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.7 ft | Not graded |
| Phosphorus | 509.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 219 µg/L | Poor |
| Trophic State Index (TSI) | 82 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 38 acres |
No bathymetric survey has been published for Lake Warnock, so its depth is not documented here.
Fishing Lake Warnock
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.1 m/yr | 2 |
| Phosphorus | ↑ Improving | -109.37 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -108.25 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Lake Warnock is a man-made reservoir impounded by the Frd No 23 (completed 1962), built primarily for flood risk reduction on the Brewery Creek; earth-type dam, 52 ft tall and 1,313 ft long.
- Surface area
- 38 ac
- Normal storage
- 24 ac-ft
- Max storage
- 2,660 ac-ft
- Drainage area
- 2.84 sq mi
- Hazard class
- High
- Owner
- ATCHISON, CITY OF
All listed purposes: Flood Risk Reduction;Fire Protection, Stock, Or Small Fish Pond;Recreation.
Source: USACE National Inventory of Dams, NID ID KS02010 · Operator website · Matched by proximity (0.09 km)
EPA Impairment Status
Lake Warnock is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit KS-LM039801 · Official waterbody report · Matched by proximity (0.18 km)
County Ranking
Ranked #2 of 2 lakes in Atchison County
Nearby Lakes in Atchison County
Frequently asked questions about Lake Warnock
Where is Lake Warnock?
- Lake Warnock is a lake in Atchison County, Kansas. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Warnock?
- Lake Warnock in Atchison County, Kansas has a water quality grade of F (Algae-prone). Water clarity: 1.7 ft visibility. Phosphorus: 509.5 µg/L. Chlorophyll-a (algae): 219 µg/L. Surface area: 38 acres.
Is Lake Warnock safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Lake Warnock is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), pesticides, pH / acidity. Check local advisories before you swim.
Explore Lake Warnock across LakeQuality
More Kansas Lake Rankings
Other Grade F Lakes in Kansas
Hypereutrophic Lakes in Kansas
Where this data comes from
10 measurements from 1 monitoring station, 2013–2017. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Kansas Department Of Health And Environment
21KAN001_WQX10 samples · 2013–2017
Analytical methods
- Depth, Secchi disk depth
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database